Microchannel hybrid evaporator

ABSTRACT

A heat exchanger including a primary inlet manifold that has an inlet port to receive refrigerant from a source, a primary outlet manifold that has an outlet port to discharge refrigerant from the heat exchanger, and a plurality of microchannel tubes fluidly connected between the primary inlet manifold and the primary outlet manifold and spaced apart from each other. Each of the plurality of microchannel tubes has a secondary inlet manifold fluidly coupled to the primary inlet manifold, a secondary outlet manifold fluidly coupled to the primary outlet manifold, and at least one microchannel fluidly coupled between the secondary inlet manifold and the secondary outlet manifold to direct refrigerant to the secondary outlet manifold. The heat exchanger also includes a plurality of fins disposed between adjacent microchannel tubes and oriented to define an airflow path along the longitudinal direction of the microchannel tubes.

RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication Ser. No. 61/486,521 filed May 16, 2011, the entire contentsof which are hereby incorporated by reference.

BACKGROUND

The present invention relates to an evaporator, and more particularly toa microchannel evaporator.

In conventional practice, many refrigeration circuits utilize anevaporator including a coil that is formed from round copper or aluminumtubing. Other refrigeration circuits utilize an evaporator that includesa coil with microchannel tubes and fins in very high densities that canonly operate at refrigerant temperatures above 32 degrees Fahrenheit dueto rapid ice buildup in the fins at temperatures below 32 degreesFahrenheit.

SUMMARY

The invention provides a heat exchanger that includes microchannel tubesand fins for use in low (e.g., −20 degrees Fahrenheit) andmedium-temperature (e.g., 26 degrees Fahrenheit) refrigerationapplications. The evaporator can achieve a discharge air temperaturethat is as close as possible to the temperature of the refrigerantinside the coil, which allows for higher refrigerant temperatures in thecoil to be used, which saves energy. The evaporator can reduce therefrigerant charge of the system by using microchannel ports inside ofthe coil rather than traditional round copper or aluminum tubes. Theevaporator can be modular or full length such that it is the samenominal length as a merchandiser. The evaporator can vary in depth,height, and width. Refrigerant may enter and exit on the same side ofthe coil, on opposite sides of the coil, or somewhere in between theends of the larger manifolds. Sandwiched between the microchannel tubesare fins which can vary in density from one to ten fins per inchdepending upon the temperature application. The fins can have a varietyof shapes (e.g., triangular, offset strips, wavy, louvered, perforated,etc.). Fin density in the evaporator can be the same or varied indifferent areas of the evaporator. Fin density can be varied along thecoil such that a lower fin density can be used at the air inlet side ofthe coil to remove moisture from an air flow. As more moisture isremoved from the air passing through the coil, higher fin densities canbe used, especially near the outlet. For low temperature applicationsfin density can be decreased as needed to accommodate buildup of frost.

In one construction, the invention provides a heat exchanger including aprimary inlet manifold that has an inlet port to receive refrigerantfrom a source, a primary outlet manifold that has an outlet port todischarge refrigerant from the heat exchanger, and a plurality ofmicrochannel tubes fluidly connected between the primary inlet manifoldand the primary outlet manifold and spaced apart from each other. Eachof the plurality of microchannel tubes has a secondary inlet manifoldfluidly coupled to the primary inlet manifold, a secondary outletmanifold fluidly coupled to the primary outlet manifold, and at leastone microchannel fluidly coupled between the secondary inlet manifoldand the secondary outlet manifold to direct refrigerant to the secondaryoutlet manifold. The heat exchanger also includes a plurality of finsdisposed between adjacent microchannel tubes and oriented to define anairflow path along the longitudinal direction of the microchannel tubes.

In another construction, the invention provides a heat exchangerincluding an inlet manifold that has an inlet port to receiverefrigerant from a source, an outlet manifold that has an outlet port todischarge refrigerant from the heat exchanger, and a plurality ofrefrigerant tubes fluidly connected between the inlet manifold and theoutlet manifold and spaced apart from each other. Each of the pluralityof microchannel tubes has a plurality of microchannels. The heatexchanger also includes a plurality of fins positioned between adjacentmicrochannel tubes and having an airflow inlet oriented to receive anairflow and an airflow outlet, the fins defining a fin density thatvaries along the length of the refrigerant tubes based on the locationof the fins relative to the airflow inlet and the airflow outlet.

In another construction, the invention provides a heat exchangerincluding a primary inlet manifold that has an inlet port to receiverefrigerant from a source, a primary outlet manifold that has an outletport to discharge refrigerant from the heat exchanger, and a pluralityof microchannel tubes fluidly connected between the primary inletmanifold and the primary outlet manifold and spaced apart from eachother. Each of the plurality of microchannel tubes has a secondary inletmanifold fluidly coupled to the primary inlet manifold, a secondaryoutlet manifold fluidly coupled to the primary outlet manifold, and aplurality of microchannels fluidly coupled between the secondary inletmanifold and the secondary outlet manifold to direct refrigerant to thesecondary outlet manifold. The heat exchanger also includes a pluralityof fins disposed between adjacent microchannel tubes. The fins have anairflow inlet oriented to receive an airflow and an airflow outlet, anddefine a first fin portion that has a first fin density and a second finportion that has a second fin density such that the density of the finsvaries along the length of the refrigerant tubes based on the locationof the fins relative to the airflow inlet and the airflow outlet.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an evaporator embodying the invention.

FIG. 2 is another perspective view of the evaporator of FIG. 1.

FIG. 3 is an enlarged view of a portion of the evaporator of FIG. 2.

FIG. 4 is a perspective view exposing a portion of the evaporator.

FIG. 5 is a cross-section view of a portion of the evaporator takenalong line 5-5 of FIG. 2.

FIG. 6 is a perspective view of another evaporator embodying theinvention.

FIG. 7 is a perspective view of a portion of the evaporator of FIG. 6.

FIG. 8 is a perspective view of another portion of the evaporator ofFIG. 6.

FIG. 9 is a side view of the portion of the evaporator of FIG. 8.

FIG. 10 is a cross-section view of a portion of another evaporatorembodying the invention.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate an evaporator 10 that can be used as part of arefrigeration system (not shown) in low-temperature refrigerationapplications (e.g., −20 degrees Fahrenheit) and medium-temperaturerefrigeration applications (e.g., 26 degrees Fahrenheit) in a retailsetting (e.g., grocery stores or supermarkets) to provide heat transferfrom the refrigerant in the evaporator 10 to air flowing through theevaporator 10. The evaporator 10 can be used in conjunction withrefrigerated merchandisers, walk-in coolers, walk-in freezers, or othercold storage spaces.

As shown in FIGS. 1-4, the evaporator 10 includes a primary inletmanifold 15 that has an inlet port 20 for receiving refrigerant, and aprimary outlet manifold 25 that has an outlet port 30 for dischargingrefrigerant from the evaporator 10. Refrigerant can enter and exit onthe same side of the evaporator 10, on opposite sides of the evaporator10, or somewhere between the ends of the manifolds 15, 25. Theevaporator 10 also includes a plurality of secondary inlet manifolds 35that are fluidly coupled to the primary inlet manifold 15, a pluralityof secondary outlet manifolds 40 that are fluidly coupled to the primaryoutlet manifold 25, and flat tubes 45 that are fluidly coupled betweenthe secondary inlet manifolds 35 and the secondary outlet manifolds 40.The secondary inlet manifolds 35 are spaced apart from each other alongthe length of the primary inlet manifold 15, and the secondary outletmanifolds are spaced apart from each other along the length of theprimary outlet manifold 25.

The flat tubes 45 can be spaced at different or varying distancesrelative to each other to maximize performance of the evaporator 10 atlow and medium temperatures. As illustrated in FIG. 5, the flat tubes 45include multiple internal passageways or microchannels 50. Generally,the microchannels 50 are much smaller in size than the internalpassageway of a conventional fin-and-tube evaporator coil. Themicrochannels 50 can be defined by any suitable cross-section (e.g.,rectangular, triangular, circular, oval, etc.) for distributingrefrigerant.

As illustrated in FIG. 3, the evaporator 10 includes a plurality of fins55 that are coupled between adjacent flat tubes 45. As illustrated, thefins 55 are oriented within the evaporator 10 to define an airflow paththat receives an airflow 60 in a generally downward direction along thelength of the flat tubes 45 (i.e., along the longitudinal direction ofthe tubes 45). In other constructions, the fins 55 can receive air fromany suitable direction. The fins 55 can have any suitablecross-sectional shape (e.g., rectangular, oval, circular, triangular,offset strips, wavy, louvered, perforated, etc.).

The fins 55 vary in density along the length of the flat tube 45. Withreference to FIG. 4, the evaporator 10 is defined by a first density finportion 65 located adjacent the secondary outlet manifolds 40, a seconddensity fin portion 70 at a central area of the flat tubes 45, and athird density fin portion 75 located adjacent the secondary inletmanifolds 35. The second density fin portion 70 is less dense than thefirst density fin portion 65, and the third density fin portion 75 isless dense than the second fin density portion 65. For example, the fins55 can vary in density from one to ten fins per inch between the firstdensity fin portion 65, the second density fin portion 70, and the thirddensity fin portion 75 depending on the temperature application. In theillustrated construction, the first, second, and third fin densityportions 65, 70, 75 do not overlap. In other constructions, the first,second, and third fin density portions 65, 70, 75 may overlap.Generally, the fins 55 can have any shape suitable for heat transfer.

FIGS. 6-9 illustrate another evaporator 110 for use in a refrigerationsystem. Except as described below, the evaporator 110 is the same as theevaporator 10 described with regard to FIGS. 1-5, and like elements havebeen given the same reference numerals.

With reference to FIG. 6, the evaporator 110 includes a single inletmanifold 115 and a single outlet manifold 120. The inlet manifold 115and the outlet manifold 120 are fluidly coupled via flat tubes 125. Asillustrated in FIG. 6, a plurality of fins 130 are coupled betweenadjacent flat tubes 125. With reference to FIGS. 7-9, the fins 130include a rectangular-shaped body portion 135 and a curved end portion140, on each end. As illustrated in FIGS. 8 and 9, the fins 130 arepositioned to receive an airflow 145. In other constructions, the fins130 may be other shapes and receive air in other directions.

FIG. 10 illustrates another evaporator 210. Except as described below,the evaporator 210 is the same as the evaporator 10 described withregard to FIGS. 1-5. In particular, the illustrated evaporator 210includes a plurality of microchannels 215 (one shown). As illustrated,the microchannel 215 has a large or over-sized cavity 220 to accommodateliquid cooling fluids (e.g., 35 percent propylene glycol).

In operation, the evaporator 10, 110, 210 functions as part of atwo-phase refrigeration system in which the evaporator 10, 110, 210receives low-pressure, low-temperature liquid refrigerant, removes heatfrom an airflow (e.g., airflow 60, 145) that passes through theevaporator 10, 110, 210, and discharges gaseous refrigerant to one ormore compressors (not shown). The low-pressure, low-temperature liquidrefrigerant evaporates as it passes through the evaporator 10, 110, 210such that the refrigerant passes through a substantial portion of theevaporator 10, 110, 210 as a two-phase mixture (i.e., a liquid-gasstate).

With reference to the evaporator 10, for example, the inlet port 20directs low-pressure, low-temperature liquid refrigerant into theprimary inlet manifold 15, which provides refrigerant to the pluralityof second inlet manifolds 35. The second inlet manifolds 35 directrefrigerant to the plurality of flat tubes 45 where the refrigerant isthen directed through the microchannels 50. The refrigerant flows fromthe microchannels 50 to the plurality of secondary outlet manifolds 40,and then to the primary outlet manifold 25 before reaching the outletport 30.

The evaporator 10, 110, 210 achieves a discharge air temperature that isas close as possible to the temperature of the refrigerant inside thecoil. The similarity in temperatures between the refrigerant and the airflowing through the evaporator 10, 110, 210 results in higherrefrigerant temperatures in the coil, which reduces energy costs becauseit is more likely that the refrigerant directed to the compressors willbe in a gaseous state. The microchannels 50, 215 minimize therefrigerant charge of the refrigeration system as compared toconventional evaporators with round copper or aluminum tubes. Theevaporator 10, 110, 210 can be modular or full length, and the size(e.g., depth, height, or width) can vary depending on the size and typeof merchandiser in which the evaporator 10, 110, 210 will be used.

The evaporator 10, 110, 210 accommodates multiple or variable findensities and microchannel tube spacing to maximize performance of theevaporator 10, 110, 210 based on the temperature application in whichthe evaporator 10, 110, 210 will be used. For example, the fin densitycan be varied in the evaporator 10, 110, 210 so that a low fin density(e.g., third density fin portion 75) is oriented at the air inlet sideof the evaporator 10, 110, 210 to remove moisture from an air flow tominimize frosting of the evaporator 10, 110, 210. As moisture is removedfrom the air passing through the evaporator 10, 110, 210, higher findensities (e.g., first density fin portion 65, second density finportion 70) can be oriented adjacent the middle and outlet-side of theevaporator 10, 110, 210. In low temperature applications, the findensity of the evaporator 10, 110, 210 can be further decreased relativeto medium temperature applications to minimize frost buildup.

The primary inlet manifold 15, 115 distributes refrigerant to themicrochannels 50, 215 so that the latent heat absorbed by therefrigerant is as high as possible without frosting the evaporator 10,110, 210. With regard to the evaporator 10, for example, the pluralityof secondary inlet manifolds 35 evenly distribute refrigerant fromprimary inlet manifold 15 to the microchannels 50. Similarly, theplurality of secondary outlet manifolds evenly distribute heatedrefrigerant from the microchannels 50 to the primary outlet manifold 35.

Various features and advantages of the invention are set forth in thefollowing claims.

1. A heat exchanger comprising: a primary inlet manifold including aninlet port to receive refrigerant from a source; a primary outletmanifold including an outlet port to discharge refrigerant from theprimary outlet manifold; a plurality of microchannel tubes fluidlyconnected between the primary inlet manifold and the primary outletmanifold and spaced apart from each other, each of the plurality ofmicrochannel tubes including a secondary inlet manifold fluidly coupledto the primary inlet manifold, a secondary outlet manifold fluidlycoupled to the primary outlet manifold, and at least one microchannelfluidly coupled between the secondary inlet manifold and the secondaryoutlet manifold to direct refrigerant to the secondary outlet manifold;and a plurality of fins disposed between adjacent microchannel tubes andoriented to define an airflow path along the longitudinal direction ofthe microchannel tubes.
 2. The heat exchanger of claim 1, wherein theplurality of microchannel tubes are spaced apart from each other alongthe length of the primary inlet manifold.
 3. The heat exchanger of claim1, wherein the microchannel tubes extend substantially vertically andthe fins are oriented such that an airflow is directed in a generallyvertical direction along the airflow path.
 4. The heat exchanger ofclaim 1, wherein the fins have one of a rectangular cross-sectionalshape, a triangular cross-sectional shape, a curved cross-sectionalshape.
 5. The heat exchanger of claim 4, wherein the fins define a findensity that varies along the length of each of the microchannel tubes.6. The heat exchanger of claim 1, wherein the fins have one of a wavyprofile, a louvered profile, and a perforated profile.
 7. The heatexchanger of claim 1, wherein the primary inlet manifold and the primaryoutlet manifold are oriented substantially horizontal, and wherein thesecondary inlet manifold is oriented at a non-zero angle relative to theprimary inlet manifold and the secondary outlet manifold is oriented ata non-zero angle relative to the primary outlet manifold.
 8. A heatexchanger comprising: an inlet manifold including an inlet port toreceive refrigerant from a source; an outlet manifold including anoutlet port to discharge refrigerant from the primary outlet manifold; aplurality of refrigerant tubes fluidly connected between the inletmanifold and the outlet manifold and spaced apart from each other, eachof the plurality of microchannel tubes including a plurality of microchannels; and a plurality of fins positioned between adjacentmicrochannel tubes and having an airflow inlet oriented to receive anairflow and an airflow outlet, the fins defining a fin density thatvaries along the length of the refrigerant tubes based on the locationof the fins relative to the airflow inlet and the airflow outlet.
 9. Theheat exchanger of claim 8, wherein the fin density of the fins locatedadjacent the airflow inlet is lower than the fin density of the finslocated adjacent the airflow outlet.
 10. The heat exchanger of claim 9,wherein the fins define a first fin portion having a first fin densityand a second fin portion having a second fin density that is lower thanthe first fin density.
 11. The heat exchanger of claim 10, wherein thefins further define a third fin portion having a third fin density thatis lower than the second fin density.
 12. The heat exchanger of claim 8,wherein the fins are oriented to define an airflow path along thelongitudinal direction of the microchannel tubes.
 13. The heat exchangerof claim 12, wherein the refrigerant tubes extend substantiallyvertically and the fins are oriented such that an airflow is directed ina generally vertical direction along the airflow path.
 14. The heatexchanger of claim 8, wherein the fins have one of a rectangularcross-sectional shape, a triangular cross-sectional shape, a curvedcross-sectional shape, a wavy profile, a louvered profile, and aperforated profile.
 15. The heat exchanger of claim 8, wherein the finsare defined by a body portion and end portions on both ends, at leastone of the end portions defining one of the airflow inlet and theairflow outlet on a face side of the heat exchanger.
 16. The heatexchanger of claim 15, wherein the fins include curved end portions onboth ends such that the airflow inlet and the airflow outlet aredisposed in at least one face side of the heat exchanger.
 17. The heatexchanger of claim 16, wherein each of the body portion and the curvedend portions are defined by a substantially rectangular cross-section.18. The heat exchanger of claim 15, wherein the airflow inlet and theairflow outlet are disposed on the same face side of the heat exchanger.19. The heat exchanger of claim 18, wherein the airflow inlet and theairflow outlet are defined by a substantially rectangular cross-section.20. A heat exchanger comprising: a primary inlet manifold including aninlet port to receive refrigerant from a source; a primary outletmanifold including an outlet port to discharge refrigerant from theprimary outlet manifold; a plurality of microchannel tubes fluidlyconnected between the primary inlet manifold and the primary outletmanifold and spaced apart from each other, each of the plurality ofmicrochannel tubes including a secondary inlet manifold fluidly coupledto the primary inlet manifold, a secondary outlet manifold fluidlycoupled to the primary outlet manifold, and a plurality of microchannelsfluidly coupled between the secondary inlet manifold and the secondaryoutlet manifold to direct refrigerant to the secondary outlet manifold;and a plurality of fins disposed between adjacent microchannel tubes andhaving an airflow inlet oriented to receive an airflow and an airflowoutlet, the fins defining a first fin portion having a first fin densityand a second fin portion having a second fin density such that thedensity of the fins varies along the length of the refrigerant tubesbased on the location of the fins relative to the airflow inlet and theairflow outlet.
 21. The heat exchanger of claim 20, wherein the firstfin portion is disposed adjacent the secondary outlet manifold and thefirst fin density is higher than the second fin density.
 22. The heatexchanger of claim 21, wherein the fins further define a third finportion disposed adjacent the secondary inlet manifold and has a thirdfin density that is lower than the second fin density.
 23. The heatexchanger of claim 20, wherein the fins are oriented to define anairflow path along the longitudinal direction of the microchannel tubes.